Welding system



Ap i 27, 1937- A E. SCHUELER 2i,78,6

WELDING SYSTEM Filed Aug. 15, 1954 WITNESSES: INVENTOR d 4 v fl/fi'edi 5C/7ue/er:

Patented Apr. 27, 1937 i UNITED STATES PATENT OFFICE 2,018,690 WELDING SYST Alfred E. Schueler, 'Wilkinshurg, Pa., assignor to ,Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania.

Application Au gust 15, 1934, Serial No. 739,89i

9 Claims. (oi. 219-8) My invention relates, generally, to welding aptherefrom at the expiration of a predetermined paratus and it has particular relation to are interval after current ceases to fiow in the welding apparatus. welding circuit.

In arc welding, it is desirable to use a source Another object of my invention is to proof welding current having a relatively high open vide for automatically connecting an arc welding 5 circuit voltage in order to readily start the weld-' circuit to a high operating voltage immediately ing arc and to maintain it in operation. In on completion of the welding circuit and for automany instances, it is desirable to use an open cirmatically disconnecting it therefrom at the excuit voltage of 100 to 140 volts. It is especially piration of a regulatable time interval after ourj 10 desirable to use such a voltage range when the rent ceases to flow in the welding circuit. 10 welding operation is to be performed with high Other objects of my invention will, in part, be

5 values of alternating current, such as 500 to 750 obvious and, in part, appear hereinafter.

amperes. My invention accordingly is disclosed in the However, the high open circuit voltage, when embodiment hereof shown in the accompanying applied to the welding circuit creates an undesirdrawing and comprises the features of construc- 15 able hazard to the welding operator and to other tion, combination of elements and arrangement workmen who may accidentally come in contact of parts which will be exemplified in the conwith it. While the welding operation is being perstruction hereinafter set forth and the scope of formed, the voltage applied to the welding cirthe application of which will be indicated in the cuit is, of course, considerably lower than the open appended claims. 20 circuit voltage and is not dangerous. However, For a more complete understanding of the as soon as the welding operation ceases, the full nature and scope of my invention, reference may open circuit voltage is applied to the welding be had to the following detailed description, taken circuit. in connection with the accompanying drawing,

It is, therefore, desirable to provide for autoin which the single figure represents, diagram- 25 matically reducing the open circuit, voltage, as matically, one concrete embodiment of my inapplied tothe welding circuit, when the welding vention. operation is not being performed. However, it According to my invention, I p vi a line is desirable to maintain the high open circuit or switch for connecting a source of relatively high operating voltage applied to the Welding circuit operating voltage, which may be the secondary for a predetermined interval afterwelding current Winding of a welding transformer, to a welding ceases to flow in order to permit the operator to circuit. The line switch is arranged to be autotake advantage of the high open circuit voltage matically closed by means of a time delay relay, characteristic of the welding source for immediwhich is energized from a low voltage tap on the ately restarting the are. In the event that the secondary winding when the welding circuit is 35 are is not restruck within the predetermined incompleted, by causing the welding electrode to terval, it is then desirable that the high open come into contact engagement with the work circuit voltage be removed from the welding forming the other electrode. As long as welding circuit. 7 current continues to flow, the time delay relay The object of my invention, generally stated, is will remain energized and the line switch will 40 to provide an arc welding system which shall remain closed. When the current in the welding be simple and efficient in operation and which circuit ceases to flow, the time delay relay is demay be readily and economically manufactured energized. However, due to its particular operand installed. ating characteristics, the time delay relay does 5 The principal object of my invention is to pronot immediately open the energizing circuit for vide for automatically connecting an arc weldthe line switch and, therefore, the latter remains ing circuit to a high operating voltage on in the closed position for a predetermined incompletion of the welding circuit and for autoterval after welding current ceases to flow. -In matically disconnecting it therefrom on cessation the event that welding current is not caused to of flow of weld ng current. flow again within the interval during which the 50 An important object of my invention is to protime delay relay remains operated, the energizing vide for automatically connectingan arc welding circuit for the line switch will be opened and the circuit to a high operating voltage immediately high operating voltage will no longer be applied on completion of the welding circuit and for to the welding circuit. I

automatically disconnecting the welding circuit Referring now particularly to the single figure -55 of the drawing, the reference character Ill designates generally a welding transformer having a primary winding H which may be connected to a source of alternating current l2. The transformer I0 is also provided with a secondary winding l3 which is connected to apply an operating voltage to a welding circuit comprising conductors l4 and I5 and to cause welding current to flow therethrough. It will be observed that the conductors l4 and I5 are connected respectively to a welding electrode l5 and work |1 between which a welding arc |8 may be maintained for performing the welding operation.

In order to connect the welding circuit comprising the conductors I4 and I5 to the secondary winding l3 of the transformer ID, a line switch 2| is provided having an operating winding 22. The line switch 2| is provided with "make contact members 23 which are arranged to connect the conductor M to one terminal of the secondary winding l3, the other terminal thereof being permanently connected to the conductor l5. The line switch 22 is also provided with break contact members 24 for a purpose which will be set forth hereinafter.

In order to effect the closure of the line switch 2| a time delay relay, shown generally at 26, is provided for energizing the operating winding 22. The time delayrelay 26 is provided with a main operating winding 21 and a neutralizing winding 28. When the main operating winding 21 is energized, contact members 29 are closed to complete a circuit for energizing the operating winding 22.

It will be noted that one of the contact members 29 is mounted on an armature 30, which may be biased by means of a spring 3|, and the tension of which may be adjusted by means of an adjusting nut 32. The tension applied to the spring 3| determines, in part, the time required for the contact members 29 to open after the main winding 21 is deenergized.

The neutralizing winding 28 is connected for energization across a potentiometer 83 which, in turn, is connected inseries circuit relation with a resistor 34. The potentiometer and series connected resistor are connected across the direct current terminals of a rectifier 35. The flux generated by the neutralizing winding 28 is in such direction as to oppose the flux which is generated by the main winding 21. There is, therefore, no residual magnetism tending to hold the armature 30 in the closed position and it is possible to adjust its opening time within certain limits, as may be desired, either by adjusting the tension of the spring 3| or by adjusting the voltage which is applied to the neutralizing winding 28 by means of the potentiometer 33.

For a more complete understanding of the characteristics of operation of the time delay relay 26, reference may be had to Patent No. 1,753,983 to Cook, patented April 8, 1930 and assigned to the assignee of this application.

It will be observed that the rectifier 35 is connected between a low voltage tap 36 on the secondary winding |3 of the welding transformer l8, and the conductor l4. Thus, when the welding electrode I6 is caused to engage the work l1, an alternating current potential is applied across the rectifier 35, which is the voltage existing between the conductor l5 and the tap 36. This voltage is rectified by the rectifier 35 and is applied in the form of direct current to the neutralizing winding 28 and to the ,main winding 21, thereby energizing the time delay relay 26 which, in turn, causes the line switch 2| to be operated.

Since the operation of the line switch 2| opens the break" contact members 24, which form a part of the energizing circuit for the main winding 21, it is necessary that means be provided for maintaining the energizing circuit for the main winding 21 as long as the welding operation is being performed. For this purpose, a current responsive relay, shown generally at 40, is provided having an operating winding 4|, which is connected to be energized from a secondary winding 42 of a current transformer. As shown the secondary winding 42 is disposed around the conductor l4, which forms a single turn primary winding. It will be observed that the current responsive relay 40 is provided with "make contact members 43 which are connected in shunt circuit relation with the break contact members 24.

In operation, it will be assumed that the welding transformer III is energized and that the full operating voltage exists across the terminals of the secondary winding l3. This voltage may be of the order of to volts, while the voltage existing between the conductor l5 and the tap 36 may be of the order of 30 to 40 volts. It will be also assumed that the remaining apparatus is in the non-operated position, as illustrated in the drawing.

Under these conditions, only a comparatively low voltage is applied to the welding circuit comprising the conductors l4 and I5, since the voltage which is applied thereto is that which exists between the conductor l5 and the low voltage tap 36. Therefore, if any person accidentally engages the welding circuit, the voltage which is encountered will not be dangerous.

The operator desiring to initiate the welding operation contacts the welding electrode I8 with the work l1. As a result, current is caused to flow through the rectifier 35 which is changed thereby into direct current, and applied to the neutralizing winding 28 and to the main winding 21. Since the flux which is generated by the main winding 21 is considerably greater than that generated by the neutralizing winding 28, the armature 30 is moved to the closed position and the contact members 29 complete an obvious energizing circuit for the operating winding 22. Contact members 23 of the line switch 2| are then closed and the full operating voltage is applied across the welding circuit.

It will be recalled that the closing of the line switch 2| opens the energizing circuit for the main winding 21 at break" contact members 24. The energizing circuit for the main winding 21, however, is maintained by the closure of contact members 43 as soon as current flows in the welding circuit due to the energization of the current responsive relay 40.

As long as current continues to flow in the welding circuit, the contact members 43 will be held in the closed position and the main winding 21 will be energized. As soon as current ceases to flow in the welding circuit, the operating winding 4| of the current responsive relay 48 is deenergized and contact members 43 are opened. The energizing circuit for the main winding 21 is then open. However, due to the time delay characteristics of the relay 28, contact members '28 are not immediately opened and, therefore,

the line switch 2| is maintained in the closed position. The contact members 29 will be held in the closed position for a predetermined inter val. If, during this interval, the Operator again causes current to flow in the welding circuit, the current responsive relay 40 is again energized and the energizing circuit for the main winding 21 is again completed.

However, if current is not again caused to flow in the welding circuit within the predetermined interval, contact members 29 will be opened at the expiration thereof, thereby opening the energizing circuit for the operating winding 22 of the line "switch 2|. 'As a result, the contact members 23 will be opened and the full operating voltage will no longer be applied to the welding circuit. When the operator desires to again initiate the welding operation, the foregoing sequence of functioning may again be caused to take place.

Since certain further changes may be made in the above construction and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the above descrip- I tion or shown in the accompanying drawing.

shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. An arc welding system comprising, in combination, an arc welding circuit connected to a welding electrode and work on which a welding operation is to be performed, a source of current for energizing the welding circuit, an electro-magnetic-switch operable to connect the welding circuit to the current source, and means including a time delay relay operable in response to the engagement of the electrode tothe work for effecting the energization and closure of said electro-magnetic switch, said time delay relay being disposed to thereafter function to hold the electro-magnetic switch closed for a predetermined interval after' the welding circuit has been opened to terminate the flow of welding current.

2. An alternating current arc welding system comprising, in combination, a source of alternating current power, a welding circuit connected to a welding electrode and work on which a welding operation is to be performed, a welding transformer connected between the power source and welding circuit, an electrically-operated line :switch for connecting the welding circuit to the secondary winding of the transformer, means including a time-delay relay operable in response to the engagement of the electrode to the work for energizing. and closing the line switch, and

means responsive to the opening of the welding;

a relatively high open circuit voltage, means for applying a portion of the open circuit voltage to the welding circuit when it is open, switch .means for automatically applying the high open circuit voltage to the welding circuit on completion thereof, and electro-magnetic time delay relay means for holding said switch means closed to continue to apply the high open circuit voltage to the welding circuit until the expiration of a predetermined time interval after the welding circuit is opened.

effecting the energization of said operating means to close the switch means thereby applying the operating voltage to the welding circuit, said time delay means being disposed tomaintain said operating means energized until the expiration of a predetermined interval after the welding circuit is opened. 1

5. An arc welding system comprising, in combination, a welding circuit connected to welding ele trodes between which an arc may be struck, a s urce of welding current for the welding circuit having a relatively high open circuit voltage, means for applying a portion of the open circuit voltage to the welding circuit when it is open, switch means for applying the high open circuit voltage to the welding circuit, operating means for said switch means, time delay means disposed to be automatically energized by application thereto of said portion of the open circuit voltage trodes adapted to strike an arc, a transformer having a primary winding for connection to an alternating current source and a secondary winding provided with a low voltage tap for connection to the welding circuit, a switch for connecting the secondary winding to the welding circuit, an operating winding for said switch, and a time delay relay interposed between said low voltage tap and the welding circuit and disposed to be energized on completion of the welding circuit, said time delay relay being disposed to efiect the energization of said operating winding to close said switch and to maintain said operating winding energized for holding said switch closed for a predetermined interval after the welding circuit is opened.

7. An arc welding system comprising, in combination, a, welding circuit including welding electrodes adapted to strike an are, a transformer having a primary winding for connection to an alternating current source and a secondary wind-= ing provided with a low voltage tap for connection to the welding circuit, a switch having make contact members for connecting the secondary winding to the welding circuit and break contact members, an operating winding for said switch, a time delay relay connected between said low voltage tap and the welding circuit through said break contact members and disposed to be energized on completion of the welding circuit for energizing said operating winding to operatesaid switch, and a current responsive relay connected tobe energized on flow of welding current and provided'with make contact members connected in parallel circuit relation with said break contact members for maintaining said time delay relay energized as long as current continues to flow in said welding circuit, said time delay relay being disposed to maintain said operating winding energized for a predetermined interval after current ceases to flow in said welding circuit.

8. An arc welding system comprising, in combination, a welding circuit including welding electrodes adapted to strike an arc, a transformer having a primary winding for connection to an alternating current source and a secondary winding provided with a low voltage tap for connection to the welding circuit, a switch having make contact members for connecting the secondary winding to the welding circuit and break contact members, an operating winding for said switch, a rectifier connected between said low voltage tap and the welding circuit, a time delay relay disposed to effect the energization of said operating winding to operate said switch, said time delay relay being provided with a neutralizing winding and a main winding, said neutralizing winding being connected to be energized by direct current from said rectifier, said main winding being connected through said break contact members to be energized by direct current from said rectifier,

and a current responsive relay connected to be energized on flow of welding current and provided with make contact members connected in parallel circuit relation with said break contact members for maintaining said main winding energized as long as current continues to flow in said welding circuit, said time delay relay being disposed to maintain said operating winding energized for a predetermined interval after current ceases to flow in said welding circuit.

9. In an alternating current arc welding system, in combination, a source of alternating current power, a welding circuit, a transformer interposed between the power source and the welding circuit, said transformer having a low-voltage tap on its secondary winding, a line switch for connecting the welding circuit across the secondary winding, a circuit connecting the low-voltage tap to the welding circuit, and means responsive to the completionof the welding circuit through the low-voltage tap connection for energizing the line switch to connect the welding circuit across the secondary winding, said means being further operable in response to a subsequent opening of the welding circuit for a predetermined time interval for eflecting the deenergization of the line switch.

ALFRED E. SCHUELER. 

